Question

Give a definition for the golf ball event horizon and the photon event horizon.

Answer 1

Golf ball event horizon: An event horizon is a boundary beyond which events cannot affect an observer. A golf ball is a stable structure that will never undergo gravitational collapse. Each golf ball remains 'visible but ever blacker' as of when it was just outside the (growing) event horizon.
if all the golf balls are present and close together, that changes things, because it means you don't have a spacetime with an isolated black hole and mass falling in, you have a spacetime with a long line of mass extending to infinity. It only applies to a single golf ball falling in, or to individual ones falling in far enough apart that they can each be considered isolated objects.

Photon event horizon:

Black holes are incredibly gravitationally intense. Not only are they so massive that even light speed is too slow to achieve escape velocity against their gravitational pull, they also bend the path of passing light around them, beyond the event horizon. If a passing photon is a bit too close, it will get trapped in orbit around the black hole. This creates what is called a "photon ring" or "photon sphere", a perfect ring of light predicted to surround the black hole, inside the inner rim of the accretion disc, but outside the event horizon.